The coating compositions of this invention are dry, free-flowing powders that may be used in fusion coating processes. "Fusion coating processes" are here defined as those coating processes in which coating powders are distributed over a substrate (which may be hot or cold); and heat, supplied from the substrate or an external source, fuses the powders into a continuous film. Examples of fusion coating processes include fluidized bed, electrostatic spraying, hot flocking (with or without electrostatic spray), and cloud chambers. When coating powders are based upon heat curing resins, as is the case of the epoxy resins of this invention, sufficient heat in excess of that required to fuse the powders must be available to cure the coatings and fully develop their physical and chemical properties.
Powder coating compositions are known in the art which produce textured or wrinkled finishes. For example, U.S. Pat. No. 4,341,819, the teachings of which are incorporated herein by reference, describes an epoxy powder coating composition useful for producing wrinkle finishes.
Current techniques in formulating textured powder coatings require balancing particle size, resin-viscosity and filler loadings to restrict the melt flow of the material thereby causing a coating surface with various degrees of orange peel or texture. Uniformity of texture is somewhat difficult to achieve and control on a consistent basis due to normal variations in raw materials and processing. Many of these formulations are difficult to apply electrostatically because of the high filler concentrations needed to produce the desired texture.
The present invention is directed to an epoxy powder composition which provides a coating of consistent texture that is relatively independent of viscosity and filler loadings. It is also directed to a powder coating composition which may contain lower levels of fillers and therefore has improved charging characteristics that minimize "fall-off" during electrostatic coating. Other advantages of the coating composition of the invention will become more apparent with reference to the following description of the invention.